Aquifer
in a Pan

Goal: To demonstrate some aspects of the interactions between
ground water and surface water. To provide a visual tool to show how water
is stored in an aquifer, and how drinking water can become contaminated
by human activities that occur near the earthís surface.

Indiana Proficiencies and Competencies:

Middle/Junior High School 1.1, 3.2, 9.2;

First year Earth and Space Science 1.1,1.5, 6.2, 7.2;

Environmental Science, Advanced 1.1, 1.5, 2.1, 6.1 and 7.1.

Materials needed:

fish bowl, large plastic storage container, or a baking pan (any clear
container with a fairly large surface area will work)

sand and/or fine gravel - a liter or two

turkey baster

square of gauze

rubber band

food coloring

unsweetened powdered drink mix

spray bottle (mister) of water

a water source

paper towels

clay (optional - any kind will work, but be aware that the clay canít
be reused after this activity.)

Procedures: Building the basic model

Prepare a simulated well by covering the end of the turkey baster
with the square of gauze and securing it with the rubber band. Set aside.

Put sand or gravel into the container and shape it into a landscape.
Make a pond in part of this landscape.

Slowly add water to the container, so that there is a visible "ground
water" layer within the sand or gravel and water in the pond.

Insert the turkey baster into the landscape for a well.

Working with the basic model:

If you pull some water out with the baster, you are simulating water
being pumped out of the ground with a pumping well. In an actual well,
the ground water level does not change significantly every time a well
pump is activated, because there is a very large reservoir of ground water
in most aquifers. In the model you can notice a drop in water level because
of the relatively small volume of water in the model and the rather large
relative volume of the turkey baster. This phenomenon can be used to demonstrate
to the student what can happen when a lot of water is withdrawn from an
aquifer that has a small relative capacity. This drop in the water
table occurs when withdrawals are greater than recharge.

How is the aquifer recharged?

Use the spray bottle of water to simulate rainfall by spraying it
on the model.

In the model, does all the simulated rain infiltrate into the ground?
Does some of it run across the surface and flow into the pond? What are
the characteristics of a natural system that would produce run-off? Infiltration?
What factors exist in a natural system that our model does not take into
account? (evaporation and transpiration)

Variations on the theme

Confining layers

This activity can be expanded to demonstrate how confining layers, like
clay layers in the soil, reduce the amount of recharge to the aquifer
from infiltrating rain. By adding a clay layer either at the surface or
slightly below the surface, the simulated rain will tend to run-off rather
than infiltrate. By burying the clay layer below the surface, but above
the water table, a spring could be simulated.

Infiltration of contaminants

Unsweetened powdered drink mix can be sprinkled on the top of the model.
Spraying the model to simulate rainfall will wash some of the coloring
from the drink mix into the ground water. (It works best if this is done
near enough to the side of the container that the "plume" is
visible through the side.)

Contaminants spilled into pond

Drop some food coloring into the pond then pump water from the well.
Did you notice any of the contamination showing up in the well water?
Relate this to something that could happen in your community.

Surface water can be most effectively studied and observed by using the
natural environment. However, here is one activity that can take the observations
of students and model them in the classroom.

Surface water and ground water

Because ground water is difficult to observe in the natural environment,
the above activities are all based on physical "models." Seeps
and springs can be observed on the sides of hills and in ravines in Indiana,
and a field trip to observe a spring would be of great benefit to all
students.

Ground water and surface water are interrelated. In most areas of
Indiana ground water flows into and feeds the streams. The evidence of
this phenomenon can be observed in July or August when no rain has fallen
in several weeks and there is water continuing to flow in the streams.
It can also be observed in winter when the ground is frozen and springs
of liquid water flow into the stream beds, or into wetland areas. Simple
measurements can be used to back up these observations. Water temperature
of streams that have baseflow contributed by ground water will consistently
be cooler in the summer and warmer in the winter than the ambient air
temperature.